Flotation of coal



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RAYMOND r. BACON, or rrrrsnunen, rnnnsitvama, ASSIGNOB TO METALS nncovmw comrm, or New roux, max A CORPORATION or MAINE.

FLQTATION No Drawing.

To all whom. it-may concern:

Be it'known that LRAYMOND F. BACON, a citizen of the United States, residing at Pittsburgh, Allegheny county, State of Pennsylvania. .have invented certain new 7 and useful Improvements in Flotation of Coal; and I do hereby declare the following each other.

The invention is'based upon the discovery that when bituminous coal or coal refuse is properly crushed and mixed with a small amount of oil or oil mixture or equivalent stances.

froth-forming agent the true coal substances can be floated and thereby removed from the slate and other constituents of a non-carbonaceous nature or even from other carbonaceous constituents than true coal, sub- The coal may berun of mine, or it may be coal refuse such as'results, for example," from coal washlng processes, as well as culm coal or coal. wastes of various kinds.

I have found it to be necessary, in the flotation of bituminous coal, to crush the coal or coal refuse to such an extent that v it wlll pass a48 mesh or smaller sieve, in ,order to securethe maxnnum-recoverv of combustible matter. I have also found that it is necessary for the reduction of the coal 1 or refuse to 'afine form to be accomplished insuch a way that the resulting particles shall have sharp angular edges, in order to secure maximum recoveries;. and I have further found that the rubbing or shearing action, such as is produced in a disk grinding, machine. and which causes arounding 1 of the particles of cOaLinhibitsthe-floating properties of the coal and atthe same time increases the ash content of the concentrate. The grinding'should accordingly beeffected,

for example, wet-,as in a. 'ball mill, or dry any suitable form of grinding machine Specification of Patented Feb. 3, 1920.

Application filed February 27, Serial No. 151,189.

which does not subject the particles to a rounding action. in order to produce a material suitable for flotation.

When the material has been thus properly ground, the combustible matter or free coal, both 111 run of mine bituminous coal and in mine or washer refuse or other waste coal material, can be more or less completely separated from the slate or other ash-forming material which it carries, as well as from certain undesirable pseudo coal constituents when present, by subjecting the finely divided material to a flotation operation. The flotation is eflected by the use of suitableoils or oil mixtures, such ascoke oven light oil, pine oil, cold-weather mixture.,' petroleum, shale and coal oils, and other oils (mineral 'or vegetable) suitable for the purpose; or by the use of other appropriate frothing agents which enable a proper froth to be produced. With certain flotation oils, acid or alkaline sol tltions of low concentration may also be employed advantageously, the effect being to improve the quality or increase the quantity of floated coal. The flotation operation can be carried out in any appropriate type of apparatus, for example, a Callow pneumatic flotation cell. 4

The coal or coal refuse (washer lwaste, bony or mine waste) to [be concentrated -'Tl1e invention will be further illustrated; Y by the following more detailed description of certain-applications thereof:

is crushed to pass a 48-mesh sieve and thoroughly mixedzwith water (about 4 to 12 parts of water for each part of coal) and ,oil or oil mixture, etc, (0.5. to 3 lbs. per 'ton of coal). The .resultin pulp is then transferred, for example, to a Callow pneumatic flotation cell and the air bubbles thereof, rising from the porous bottom of the cell,

through the'pulp, carry up with themthe particles of. free coaland appear-on the surface as an ephemeralfoa-m which, constantly renewedffl'ows continuously over the cell -wall into .the launder. 'The foam orfroth carries with it most of the combustible matter of the coal treated, whereas the tailings are largely. composed of non-combustible --matter, the combustible matter present gave the following results:

dependent upon the oil or like agent used and the pressure of the air supplied. to the cell. Where it is desirable .to add an acid. or alkali or salt, the same can be added to the water to produce, for example, a 0.1'% solution or less, depending upon the requirements of the oil used.

The following are resultsbbtained by the treatment of coal material as described above using pine oil as the active frothing agent:

refuse was crushed to pass a LS-mesh sleve, thoroughly mixed with four parts by weight of water and pine oil in the proportion of about 1 lb. per ton of refuse, and floated in a Callow pneumatic flotation cell, collecting the froth which ran over the cell Walls into the launder. The following results were obtained:

Ash-free Recovo t te 257 25$ z zi' 7 0110511 Pa S 5 7 Tailings my; s0.5%

(2) A similar treatment of the. same material using 1.5 lbs. of pine oil 'per ton of refuse gave the following results Ash-free Recov o t t 31 e ai ii ri'y si t "7 011C911 1'8 88 Tailings 68.4% 8...l2Z: 100.0%

collecting the froth which ran over the cell walls. The following results were obtained Ash-free coal. 87.3%

Recovcry. 97 9% A Ash.

0 t t 4.8 1. Tara 4) A similar treatment of the same materlal using 12 parts of water to 1 of coal Ash-free Recovc t t A 94 s7 9 7 011081! T8 65 u Tailings: 5.29% 66.587;

The refuse and bituminous coal from which the above results were. obtained'were I found to have the following 'ash and free coal contents,

,\ Ashinrefuse... v

Ash-free coal in refuse (by 065515655511 Ash in coal 10 Ash-free coal in coal Qby difierencey'.

As stated above, the nature and quantity of the coal floated is dependent upon the manner in which the coal has been ground or crushed. The importance'of proper crush- ;ing will be apparent from the following results obtained with two samples-bf the same coal refuse ground or crushed to substantially the same size and treated'in the same manner with the same amount of oil. The

- marked luster the results being as follows:

A sample of bituminous coal washer A sample marked (1) was crushed to pass a LS-mesh sieve and showed particles with sharp angular edges. and lustrous faces; while the sample marked (2) was passed through a' disk grinding machine and showed more or less rounded grains without Ash in Ash- Concenconcenfree 1 A A v l iii c i 7.

Screen analyses of the two samples showed I that they were not essentially different as regards size of particles. The importance of proper grinding, and the production of particles of proper character will thus be evident. A v

' The concentration of coal by flotation; ac-

cording to the present invention,enables coal constituents to be recovered from coal refuse which is not commonly considered capable of further concentration by the usual methods of concentration. Thus the wastes from the w-asheries, containing the rejected material from the usual'washing process, and

. being relatively low in carbonaceous matter, can be eflectively concentrated by. the process of the present invention. Moreover, not

,only the common gangue constituents but also the bony coal, slate, schist, shale, and

- other non-carbonaceous or non-bituminous mineral substances can separated fromtrue 'coal substances.

The process of thepresent. invention is moreover adapted for the reduction of the ash content of run of mine coals, as a substitute forthe ordinary washing processes, and other processes of concentration, for the separation of non-coal substances from true coals which are contaminated therewith.

eluding culm coal; and bituminous matter suitable foruse as a fuel c'anbe separated from coal mine or washer Wastesofhigh ash content, fuel material being thus produced from high ash substances. It is economically feasible, by the process of the present invention, to recover usable coals from present unusable wastes from coal mines and washers. It is even possible to separate difl'erent coal constituents from each other in the manner above described.

The coal concentrate produced according to the present invention may be used directly as a boiler fuel, or it may be'further pulverized, after drying, for use as pow-' v tailings and used over again, where'such use is desired. When the flotation. process is Similarly the coal can be recovered from 1 mine or washer wastes of all classes, m-

operated in connection with coal'washers,

" ing operation.

-the water serves as a the water accompanying. the washer refuse may be utilized in the subsequent crushing and flotation operation, above described.

It is of great importance that the flotation of the comminuted finelyuct should take place before the surfaces of the coal particles lose the physical characteristics imparted to them by the comminut- For this reason if the comminution is effected while the coal is dry,

the flotation should preferably follow im-.

mediately, or at least before atmospheric or other influences materially dull or other- Wise prejudicially change or alter the surfaces. If the comminution is effected in the presence of Water, as in the ball mill, protective. agent as against alteration for a considerable time, and a similar temporary protection would be afforded by wetting coal that has been comminuted in the. dry state. Apparently,

killing of the luster of *the surfaces of the 1 divided prod.-'

coal particles is due to oxidation thereof, and it should usually be guarded against in the practice of the invention, to obtain the' best results 7 What I claim is:

1. The method of concentrating bituminous coal, which comprises comminuting the bituminous coal to produce a finely divided product with particles having sharp angular edges and fresh lustrous. surfaces, and subjecting the resulting product to separatign by froth flotation. v Q 7 2. The method of concentrating coal which comprises comminuting bituminous coal washer refuse to produce a finely divided product with particles having sharp angular edges and fresh lustrous surfaces,

and subJecting the resulting product'toseparation by froth flotation.

In testimony whereof I aflix my signature.

RAYMOND F. BACON. 

